JP5216739B2 - Charged particle beam apparatus and film thickness measuring method - Google Patents

Description

  The present invention relates to a charged particle beam apparatus capable of monitoring a film thickness.

  There is a growing need for inspection and analysis of semiconductor devices that are becoming increasingly miniaturized. Among them, in the failure analysis for specifying the cause of the failure, it is an essential technique to directly observe the defects inside the device. For these observations, it is necessary to precisely machine the observation target position of the device. Conventionally, a focused ion beam (hereinafter referred to as FIB) processing apparatus has been used as an apparatus for performing this precise microfabrication. In this FIB, a target position can be accurately processed by performing electrostatic deflection scanning with an ion beam focused on the submicron order and irradiating the sample. For this reason, the FIB is used for forming a cross section for analysis, producing a sample for analysis, and the like.

  For high-resolution observation, a transmission electron microscope (hereinafter referred to as TEM), a scanning transmission electron microscope (hereinafter referred to as STEM), or the like is used. In order to observe a sample with this TEM or STEM, it is necessary to process the sample thinly to a thickness that allows transmission of an electron beam, for example, about 100 nm. With the recent miniaturization of devices, it is important to control the film thickness of the sample thin film in order to prepare the sample so that the observation target position accurately enters the thin film sample.

  As a technique for monitoring the thickness of the thin film, for example, there is a technique described in Japanese Patent No. 3223431 (Patent Document 1) and Japanese Patent No. 3221797 (Patent Document 2). In these methods, the thin film processed by FIB is irradiated with an electron beam, and the thickness of the processed thin film is monitored by detecting the amount of transmitted electrons. Japanese Patent No. 3119959 (Patent Document 3) discloses that a thin film processed by FIB is irradiated with an electron beam, the irradiation intensity and transmission intensity of the electron beam are detected, and the film thickness is monitored from this intensity ratio. Have been described. In JP-A-2006-127850 (Patent Document 4), a thin film processed by FIB is irradiated with an electron beam, and a desired film thickness is determined from a change in signal luminance detected by a transmission electron detector or a scattered electron detector. It is described to do.

Japanese Patent No. 3223431 Japanese Patent No. 3221797 Japanese Patent No. 3119959 JP 2006-127850 A

  As a result of intensive studies on the film thickness monitor by the present inventor, the following findings have been obtained.

  Use of an electron beam for film thickness monitoring of a processed sample is very effective because film thickness information on a local region can be obtained. However, even with the same film thickness, the amount of transmitted electrons varies depending on the material constituting the sample. For this reason, in order to obtain accurate film thickness information, a film thickness calculation means taking into account sample material information is required.

  Moreover, since the irradiation amount of the electron beam to be irradiated varies depending on the state of the electron source, it is not necessarily constant. Due to this change in irradiation amount, the amount of transmitted electrons also varies. For this reason, in order to obtain accurate film thickness information, a film thickness calculation means capable of canceling the influence of the dose change is necessary.

  An object of the present invention is to provide a charged particle beam apparatus capable of suppressing an error due to an external condition and accurately monitoring a film thickness.

  The present invention irradiates a sample with an electron beam, individually detects a signal for each region according to the scattering angle of a transmission electron beam, calculates the individual signal intensity from each other, and calculates an accurate film thickness. About.

  According to the present invention, a thin film sample can be processed into an accurate film thickness, and the accuracy of structural observation, elemental analysis, and the like can be improved.

The figure which shows the structural example of a charged particle beam apparatus. The figure which shows the structural example of a concentric circular division | segmentation type | mold transmission electron detector. The figure which shows the structural example of a line-type division | segmentation type | mold transmission electron detector. The figure which shows the mode of light-receiving of the sample transmission electron to a division | segmentation type | mold transmission electron detector. The figure explaining the spread of the sample transmission electron of a thick sample. The figure explaining the spread of the sample transmission electron of a thin sample. The figure which shows the film thickness dependence of the signal strength by the light-receiving area | region of a transmission electron detector. The figure which shows the film thickness dependence of the signal strength normalized by the light reception area | region of a transmission electron detector. The figure which shows the film thickness dependence of BF1 signal intensity | strength by irradiation electron beam intensity change. The figure which shows the film thickness dependence of the DF3 signal intensity | strength by irradiation electron beam intensity change. The figure explaining the film thickness dependence of a division signal, and film thickness calculation. The figure explaining the spread of the sample transmission electron of the material sample with small atomic weight. The figure explaining the spread of the sample transmission electron of the material sample with a large atomic weight. The figure which shows the film thickness dependence of BF1 signal intensity | strength by the difference in a sample structural element. The figure which shows the film thickness dependence of the BF2 signal intensity | strength by the difference in a sample structural element. The figure explaining suitable light-receiving region selection of a transmission electron detector. The figure explaining suitable light-receiving region selection of a transmission electron detector. The figure which shows the element mapping image of a process sample. The figure which shows the element input method of a process sample. The figure which shows the example of the numerical film thickness display by cursor point specification. The figure which shows the example of the meter film thickness display by cursor point designation | designated. The figure which shows the example of the pop-up film thickness display by cursor point specification. The figure which shows the example of the numerical film thickness display by area | region designation. The figure which shows the example of the meter film thickness display by area | region designation. The figure which shows the example of the pop-up film thickness display by area | region designation. The figure which shows the example of a film thickness mapping image display. The figure which shows the example of GUI display of the light reception area | region of a transmission electron detector. The figure which shows the example of GUI display of multiple area | region addition of the light reception area | region of a transmission electron detector. The figure which shows the structural example of the charged particle beam apparatus with a micro sample piece extraction function. The figure explaining the extraction procedure of a micro sample piece. The figure explaining the thin film processing of a micro sample. The figure which shows the structural example of the charged particle beam apparatus with a gas ion beam. The figure explaining the finishing process by a gas ion beam.

  In an embodiment, an electron beam optical system that irradiates an electron beam, a sample stage on which a sample is placed, a transmission electron detector that detects a transmission electron in which a detection unit is divided into a plurality of regions, and a plurality of regions Disclosed is a charged particle beam apparatus comprising: an arithmetic mechanism that calculates an intensity ratio between a transmission electron beam detected by a first region and a transmission electron beam detected by a second region; and a display device that displays a film thickness of the sample. To do.

  In the embodiment, the electron beam optical system irradiates the sample with an electron beam, and the detection unit detects the transmitted electron beam transmitted through the sample with a transmission electron detector divided into a plurality of regions. A film thickness measurement method for a sample that calculates the intensity ratio of the transmission electron beam detected by the first region and the transmission electron beam detected by the second region in the plurality of regions, and displays the film thickness of the sample by a display device Is disclosed.

  Further, the embodiment discloses that the transmission electron beam intensity detected by the region detecting the transmission electron beam having a small scattering angle is divided by the transmission electron beam intensity detected by the region detecting the transmission electron having a large scattering angle. .

  In the embodiment, when the transmission electron beam detection detected by the first region and / or the second region becomes a predetermined condition, the first region and / or the second region is performed. Is disclosed.

  Moreover, in an Example, changing the said 1st area | region and / or the said 2nd area | region based on the structural element of the sample in the location irradiated with the electron beam is disclosed.

  Moreover, in an Example, providing the spectroscopic detector which detects the structural element of a sample is disclosed. Preferably, the spectral detector is an X-ray detector.

  In the embodiment, an input device for inputting constituent elements of a sample is disclosed. Moreover, it discloses that the constituent elements of the sample are input to the arithmetic device by the input device.

  Moreover, in an Example, displaying the average film thickness in the desired area | region of a sample is disclosed.

  In addition, the embodiment discloses displaying the film thickness distribution in a desired region of the sample.

  In the embodiments, a charged particle beam apparatus including an ion beam optical system that irradiates a sample with an ion beam is disclosed. In addition, it is disclosed that a thin film is formed on a sample by irradiating the sample with an ion beam by the ion beam optical system.

  In addition, the embodiment discloses that ion beam irradiation is controlled based on the output of a calculation mechanism.

  Further, in the embodiment, a charged particle beam apparatus capable of simultaneously irradiating an ion beam and an electron beam is disclosed. Moreover, it discloses that the thin film formation on the sample by ion beam irradiation and the thin film measurement by electron beam irradiation are simultaneously performed.

  In addition, the embodiment discloses a charged particle beam apparatus including a transfer mechanism that transfers a sample piece separated from an original sample by ion beam processing. Moreover, measuring the film thickness of the sample piece isolate | separated from the original sample by ion beam processing is disclosed.

  The above and other novel features and effects will be described below with reference to the drawings. The drawings are used for understanding the invention and do not reduce the scope of rights. In addition, the embodiments can be appropriately combined, and this combination is also disclosed in this specification.

  In this embodiment, a charged particle beam apparatus capable of accurately monitoring the film thickness of a sample processed with an ion beam will be described.

  FIG. 1 shows a configuration example of a charged particle beam apparatus. The charged particle beam apparatus according to the present embodiment includes a movable sample stage 102 on which the sample 101 is placed, a sample position control device 103 that controls the position of the sample stage 102 in order to specify the observation or processing position of the sample 101, An ion beam optical system 105 that performs processing by irradiating the sample 101 with the ion beam 104, an ion beam optical system controller 106 that controls the ion beam optical system 105, and secondary electrons that detect secondary electrons from the sample 101. It has a detector 107. The secondary electron detector 107 is controlled by the secondary electron detector control device 108. The electron beam optical system 110 that irradiates the sample 101 with the electron beam 109 is controlled by the electron beam optical system controller 111. The transmission electron detector 113 that detects the transmission electron beam 112 transmitted through the sample 101 is controlled by the transmission electron detector control device 114. The X-ray detector 115 that detects X-rays excited from the sample 101 by irradiation with the electron beam 109 is controlled by the X-ray detector control device 116. The sample position control device 103, the ion beam optical system control device 106, the secondary electron detector control device 108, the electron beam optical system control device 111, the transmission electron detector control device 114, the X-ray detector 115, etc. It is controlled by the device 117. As the central processing unit 117, for example, a personal computer or a workstation is generally used. In addition, a display device 118 that displays an output from the central processing unit 117 is provided. The sample stage 102, the ion beam optical system 105, the secondary electron detector 107, the electron beam optical system 110, the transmission electron detector 113, the X-ray detector 115, and the like are disposed in the vacuum container 119. With this configuration, the ion beam 104 formed by the ion beam optical system 105 is processed by irradiating the sample 101 placed on the sample stage 102, and the thickness of the sample 101 is determined by a signal from the transmission electron detector 113. Monitor.

  In the charged particle beam apparatus according to the present embodiment, the ion beam optical system 105 is arranged in the vertical direction and the electron beam optical system 110 is arranged in the oblique direction. However, the arrangement form of the optical system is not limited to this. . For example, the ion beam optical system 105 may be disposed in an oblique direction, and the electron beam optical system 110 may be disposed in a vertical direction. Further, both the ion beam optical system 105 and the electron beam optical system 110 may be arranged obliquely.

  Here, a specific configuration example of the transmission electron detector 113 will be described. FIG. 2 shows a detector having a detection region divided into concentric circular regions. Here, an example in which the area is divided into five areas 201 to 205 is shown, but this embodiment can be implemented as long as it is divided into two or more areas. The position of the detector 206 is controlled by the transmission electron detector control device 114 of FIG. 1 so that the position directly irradiated with the electron beam 109 when the sample 101 is not present is located in the central region 201 of the detector 206. Position to. The wiring 207 and the like are used to send signals in each region to the transmission electron detector control device 114. The detector 206 is composed of, for example, a semiconductor detector. In this case, the regions 201 to 205 are insulated from each other so that signals are not mixed with each other. When the transmission electron beam 112 is irradiated to the semiconductor detector, electron-hole pairs depending on the energy of electrons are formed. For example, in the case of a silicon semiconductor detector, the generation energy of electron-hole pairs at room temperature is about 3.6 eV. Therefore, if the energy of the transmission electron beam 112 is 30 kV, about 8000 electrons with one electron. -Hole pairs will be generated. This electron-hole pair is detected as a current through the wiring 207, and the amount of transmitted electrons is monitored. The detector 206 does not necessarily need to be formed in one layer. For example, a hole is formed in the region 201 and a detector is provided in the second layer, so that only electrons passing through the hole in the first layer are accurately detected. It is also possible to detect it. Moreover, it does not necessarily have to be concentric as shown in FIG. For example, as shown in FIG. 3, the region 301 is composed of regions 301 to 305, and the region 301 is positioned so as to correspond to the region 201 of FIG. You may make it detect. In the case of this structure, there is an advantage that the structure is simple and it is easy to arrange in a narrow space. On the other hand, the concentric circular shape of FIG. 2 has an advantage that the amount of signal on the outside is large.

  How the transmission electron beam 112 transmitted through the sample 101 is irradiated to the detector 206 will be described with reference to FIG. FIG. 4 is a view of the detector 206 as seen from a cross section passing through the center thereof. The electron beam 109 irradiated to the sample 101 becomes a transmission electron beam 112 spread by the interaction with the sample, and is irradiated to each region 201 to 205 of the detector 206. Among these, the electron beam irradiated to the area | region 201 near the center is the electron beam which permeate | transmitted comparatively without receiving the influence of the scattering in the sample 101. FIG. A sample obtained by imaging a sample with a signal that is not relatively scattered is generally called a bright field image (hereinafter referred to as a BF image). On the other hand, the electron beam applied to the outer region 205 is an electron beam that has been greatly scattered in the sample 101. A sample obtained by imaging a sample with a signal greatly scattered is generally called a dark field image (hereinafter referred to as a DF image). However, the boundary between BF and DF is not physically determined but relative. For example, in this embodiment, for convenience, the areas 201 and 202 are BF, and the areas 203 to 205 are DF. The area 201 is BF1, the area 202 is BF2, the area 203 is DF1, the area 204 is DF2, and the area 205. Will be referred to as DF3.

  Here, the relationship between the transmission electron beam distribution and the film thickness of the sample will be described with reference to FIGS. FIG. 5 shows a comparatively thick sample. In this case, since the electron beam 109 interacts with many atoms while passing through the sample 501, the probability that the electron beam is scattered becomes relatively large, so that the transmitted electron beam 502 spreads and is more outward. This region 205 is also irradiated with many electron beams. On the other hand, when the sample 601 is relatively thin as shown in FIG. 6, since the interaction with the sample atoms is small, the probability that the electron beam goes straight is relatively large. The signal intensity increases. In FIGS. 5 and 6, the irradiation area is expressed as if it is an electron beam boundary line. However, the electron beam is not irradiated only on the inner side. As a comparison, whether the inner intensity tends to increase or not is merely expressed in a visually easy-to-understand manner, and actual electron beams are distributed in a certain proportion in the regions 201 to 205.

  7 and 8 show the film thickness dependence of the signal intensity depending on the light receiving region of the transmission electron detector. FIG. 7 representatively shows signal strength 701 of BF1 (signal of region 201) and signal strength 702 of DF3 (signal of region 205) in an easy-to-understand manner. As described in FIGS. 5 and 6, the signal intensity 701 of BF1 increases as the film thickness decreases (goes to the left on the graph), while the signal intensity 702 of DF3 decreases (the left side on the graph). To go down). FIG. 8 also shows five regions, and each signal is normalized by a signal amount of a certain film thickness T0. In this case, the BF1 signal strength 801 monotonously increases as the film thickness decreases, the BF2 signal strength 802 has a peak in the middle of the film thickness decrease, and the DF1 signal strength 803, the DF2 signal strength 804, and the DF3 signal strength 805 are films. It decreases monotonically due to the decrease in thickness. However, as will be described later, this tendency depends on the element and changes. For example, it is necessary to understand that DF1 does not necessarily decrease monotonously due to a decrease in film thickness, but in the case of a certain element (for example, silicon), it decreases monotonically as shown in FIG. This series of explanations is performed under the condition that a certain element (for example, silicon) has the tendency shown in FIGS. Here, if the tendency of FIG. 7 is guaranteed, the film thickness can be calculated backward from the signal value of BF1, for example. However, the absolute value of the signal intensity 701 varies depending on the intensity of the electron beam 109. The intensity of the electron beam 109 varies depending on the conditions of the electron beam optical system 110 in FIG. Although the electron beam intensity change due to what can be controlled by the electron beam optical system controller 111 such as the lens intensity can be estimated to some extent, the electron beam intensity often fluctuates due to an unexpected change in the state of the electron source, etc. It is very difficult to keep the electron beam intensity constant. For this reason, when the irradiation electron beam intensity becomes weak, the signal intensity of the BF1 signal decreases from a signal intensity 901 to a signal intensity 902 as shown in FIG. In this case, even if the BF1 signal can be acquired, the correct film thickness cannot be calculated because it is not known which of the signal intensity 901 and the signal intensity 902 is correct.

  In order to detect the intensity fluctuation of the irradiated electron beam, if the change of the electron beam 109 is acquired by blocking the electron beam irradiation to the sample 101 and acquiring the change of the electron beam 109, the transmission signal cannot be acquired simultaneously. Real-time film thickness monitoring becomes impossible. In addition, when a detector is mechanically inserted between the electron source and the sample, it takes time for mechanical insertion. Although a method of largely deflecting an electron beam using electromagnetic deflection and irradiating the irradiation electron detector with the electron beam is conceivable, the large electron beam deflection causes the irradiation position shift at the time of subsequent re-irradiation of the sample. there is a possibility. For this reason, there is a need for a method that suppresses the film thickness calculation error due to the intensity fluctuation of the irradiated electron beam without acquiring the intensity fluctuation of the irradiated electron beam.

  Here, focusing on the DF3 signal, as shown in FIG. 10, when the intensity of the irradiated electron beam decreases, the signal intensity decreases from the signal intensity 1001 to the signal intensity 1102. At this time, the reduction ratio from the signal intensity 901 to the signal intensity 902 due to the decrease in the amount of irradiated electrons is equal to the reduction ratio from the signal intensity 1001 to the signal intensity 1002. Therefore, if the BF1 signal is divided by the DF3 signal, the fluctuation of the electron beam 109 can be canceled. A graph of the film thickness dependence of this division signal is shown in FIG. As described above, the effect of fluctuations in irradiation electron intensity can be ignored by dividing. Further, since the BF1 signal, the DF3 signal, and the like can be simultaneously acquired by the detector of FIG. 2, it is possible to acquire the division result in real time with irradiation. Further, as shown in FIG. 8, BF1, whose signal monotonously increases as the film thickness decreases, is monotonously decreased and divided by DF3 having the largest rate of change, so that it is steeper than any signal shown in FIG. Can be obtained. That the signal changes sharply with respect to the film thickness means that the film thickness resolution becomes higher. That is, if the obtained BF1 / DF3 intensity is A, the film thickness T can be calculated with high accuracy.

  However, as described above, since the relationship between the sample film thickness and the transmission electron beam is established for a specific element, the constituent elements of the sample are considered in calculating the sample film thickness from the transmission electron beam. There is a need. The relationship between the transmission electron beam distribution and the sample constituent elements will be described with reference to FIGS. FIG. 12 shows a case of a relatively light element sample (having a small atomic weight). In this case, since the electron beam 109 interacts with light atoms while passing through the sample 1201, the probability that the electron beam is scattered becomes relatively small. Since the probability that the transmission electron beam 1202 goes straight is relatively large, the signal intensity of the region 201 and the region 202 near the center is increased. On the other hand, when the sample 1301 is a relatively heavy element (having a large atomic weight) as shown in FIG. 13, the interaction with the sample atom is large, so that the electron beam is relatively spread, and the outer region 205 has a large amount. An electron beam will be irradiated. In FIG. 12 and FIG. 13, the irradiation area is expressed as if it were the boundary line of the electron beam. However, the electron beam is not irradiated only on the inner side, and the sample constituent elements are light. As a comparison of the heavy one, it is merely expressed visually whether the inner strength tends to become stronger or not, and the actual electron beams are distributed in a certain ratio in the regions 201 to 205.

  14 and 15 show the film thickness dependence of the signal intensity due to the difference in the sample constituent elements. FIG. 14 shows the signal strength of BF1 (the signal of the region 201). In FIG. 14, the signal intensity 1401 when the sample material is carbon (atomic weight 12.01), the signal intensity 1402 when silicon (atomic weight 28.09), and the signal intensity 1403 when tungsten (atomic weight 183.9) are shown. Show. As described with reference to FIGS. 12 and 13, it can be seen that the signal amount decreases as the atomic weight increases. Next, the signal intensity of BF2 (the signal of the region 202) is shown in FIG. The signal intensity 1501 of carbon and the signal intensity 1502 of silicon have a peak in the middle. For this reason, if this BF2 signal is used in the film thickness monitor, for example, in the case of carbon, for one signal intensity A, two film thicknesses T1 and T2 are calculated backward, and it cannot be determined which is correct. This occurs when there is a peak in the middle even when the signal division as described with reference to FIG. 11 is used. On the other hand, in the case of tungsten, since the signal intensity 1503 of BF2 does not have a peak in the middle, it can be used for film thickness monitoring. Thus, the usable area and the unusable areas 201 to 205 vary depending on the constituent elements of the sample. However, when two film thicknesses T1 and T2 are calculated as in the above-described BF2 signal of carbon, if there is a region of another element in the vicinity, a rapid film thickness distribution does not occur by ion beam processing. It is also possible to calculate the film thickness by filtering or the like that selects the one closer to the film thickness calculation result in the vicinity of another element from the preconditions. That is, it is important to select an optimum region to be used for film thickness monitoring from the regions 201 to 205 depending on the constituent elements of the sample. For example, FIG. 16 shows the case of carbon, but the signal strength 1601 of DF3 (the signal of the region 205) is nearly zero in the thin region 1602. In this case, if this DF3 signal is used as a denominator as shown in FIG. 11, it diverges and the film thickness cannot be monitored. On the other hand, the signal strength 1603 of the inner DF2 (the signal of the region 204) has a sufficient signal strength even in the thin region 1602, and is desirably used as a denominator of division instead of DF3 of FIG. Thus, for example, in a region where an actual signal is smaller than a predetermined signal intensity Ac, a method of using another region (for example, an inner region) as a denominator is very effective. In this case, a region to be used for division may be determined in advance with respect to the element, and a method of changing the region when the signal intensity Ac becomes smaller than the predetermined signal intensity Ac is also possible. Similarly, FIG. 17 shows an example of a problem in the case of tungsten. The signal intensity 1701 of BF1 (the signal of the area 201) is almost zero in the thick area 1702. In this case, as shown in FIG. 11, when this BF1 signal is used for the numerator, the signal becomes almost zero and the film thickness cannot be monitored. On the other hand, the signal intensity 1703 of BF2 (the signal of the area 202) on the outermost side has a sufficient signal intensity even in the thick area 1702, and it is desirable to use it for the numerator of division instead of BF1 in FIG. Thus, for example, in a region where the actual signal is smaller than a predetermined signal intensity Aw, a method of using another (for example, the outer) region for the molecule is very effective. In this case, a region to be used for division may be determined in advance for the element, and a method of changing the region when the signal intensity becomes smaller than a predetermined signal intensity Aw is also possible.

  Selection of the signal intensity based on the above element information requires obtaining element information before film thickness monitoring. Element information can be obtained from the signal of the X-ray detector 115 of FIG. 1, for example. That is, by irradiating the sample 101 with the electron beam 109 and detecting X-rays generated from the irradiated region, the element in the region can be specified. By scanning, an element mapping image as shown in FIG. 18 can be acquired. Here, for example, colors are displayed for each element, and the regions 1801, 1802, 1803, 1804, and 1805 are composed of different elements. Although not shown here, the content density for each element may be displayed by contrast or the like. Since the X-ray detection for acquiring the mapping image and the signal detection of each of the regions 201 to 205 in the transmission electron beam detector of FIG. 2, for example, can be performed at the same time, the element information is acquired and the optimum By selecting a detection area from the areas 201 to 205 and performing arithmetic processing, it is possible to calculate the film thickness almost in real time. Although element information acquisition by X-ray detection is described here, element information can be obtained in the same manner even when other means such as electron energy loss spectroscopy or reflection electron energy spectroscopy is used. Is available.

  In some cases, the constituent element of the sample 101 is known by design, such as a semiconductor device. In this case, the element can be designated in advance by the user. For example, the region 1901 and the region 1902 in FIG. 19 are designated on the GUI on an image formed by secondary electrons, reflected electrons, or transmitted electrons by scanning with the electron beam 109. For example, the constituent elements of the region 1901 The user inputs in the input area 1903. In this example, silicon (Si) is selected from the pull-down menu. In this way, for example, in order to monitor the film thickness of the region 1901, the optimum detection region for silicon can be automatically selected from the regions 201 to 205 (for example, the region 201 for the numerator and 205 for the denominator are selected). It becomes possible. As described above, the X-ray detector 115 and the X-ray detector control device 116 of FIG. 1 can be removed from the apparatus configuration by manually inputting the element species.

  In the above, in order to simplify the explanation, it is assumed that the energy of the irradiated electrons is constant (for example, 30 kV), but actually, the energy of the irradiated electrons can be changed. Actually, the amount of transmitted electrons varies depending on the energy of irradiated electrons, and the signal ratio itself of the regions 201 to 205 of the detector 206 also varies. That is, the signal intensity shown in FIG. 7, FIG. 8, FIG. 9, FIG. 10, FIG. 11, FIG. As a tendency, if the energy of the irradiated electrons is lowered, the signal intensity of the entire transmitted electrons is also lowered, but the regions 201 to 205 are not lowered at the same rate, and the amount of transmitted electrons on the region 201 side (near the center) is reduced. The reduction is greater. For this reason, when changing the energy of irradiated electrons, the calibration curve corresponding to FIGS. 7, 8, 9, 10, 11, 14, 14, 15, 17, etc. is also changed. It is desirable that the areas 201 to 205 to be used are also changed depending on the energy of the irradiation electrons. However, the policy for selecting the optimum region for the calculation is the same as that described above. When dividing by selecting the region with the highest rate of change for the signal that increases monotonically with the decrease in film thickness and the region with the highest rate of change with the signal that decreases monotonically with respect to the decrease in film thickness, Since it is possible to obtain a signal that is sensitive to changes in thickness, it is optimal for region selection. However, in the region or element in which the signal intensity becomes too small, changing the region selection to the second candidate region is the same as described above. In this way, an accurate film thickness monitor can be realized even when the energy of irradiated electrons is changed.

  Here, FIGS. 20 to 26 show the display method of the film thickness when the film thickness information is acquired by the above method.

  A secondary electron image 2001 in FIG. 20 is a cross-sectional image of the sample 101. Although a secondary electron image is used here, the sample is not limited to a secondary electron image, and may be a transmission electron image, a reflection electron image, an element mapping image, or the like. An image of 101 is desirable. This is because the position error of the region designated for the film thickness monitor does not occur because it has the same deflection scanning information as the electron beam 109 used for the film thickness monitor. Here, when the position where the film thickness is desired to be monitored is designated by the cursor 2002, the film thickness calculated by the above method is displayed in the film thickness display area 2003.

  Further, the meter display area 2101 of FIG. 21 is configured so that a needle that can swing the film thickness value at the cursor position is shown. By moving the cursor on the secondary electron image or the like and observing how the needle moves due to the movement of the cursor, the change in film thickness depending on the position can be visually recognized. Further, when the film thickness is monitored simultaneously with the processing by the ion beam 104 using the meter display area 2101, it is possible to visually recognize the state in which the film thickness is decreased by the processing by the shake of the meter needle. Easy to understand the situation.

  Further, a pop-up display as shown in FIG. 22 is also possible. A pop-up 2201 is a balloon displayed near the cursor position, and displays the film thickness corresponding to the cursor position such as a secondary electron image as a numerical value inside the balloon. Thereby, the film thickness can be recognized without taking the eyes off the secondary electron image 2001.

  The display of the film thickness information at the point indicated by the cursor has been described above, but there is a case where it is desired to know the average information of the area having a certain area. This display example is shown in FIGS.

  FIG. 23 shows an example of numerical film thickness display by region designation. A monitor area 2301 in FIG. 23 is an area where information is averaged, and the size and position can be changed. For example, the size can be set by a drag operation, and the position can be changed by a cursor, a cross key on the keyboard, or the like. The film thickness in this area is displayed in the film thickness display area 2302. Note that a meter display as shown in FIG. 24 or a pop-up display as shown in FIG. 25 may be used. In the cross-section processing of the ion beam, a sharp in-plane film thickness change hardly occurs. Therefore, particularly when measuring the film thickness produced by the ion beam, when such an area average film thickness display is used, FIG. More stable information than the point data as shown in FIG. 22 can be obtained.

  Further, for example, as shown in FIG. 26, the calculated film thickness is assigned to contrast, pseudo color, or the like, and the film thickness distribution of the region corresponding to the secondary electron image or the like is changed by contrast change or color change. It may be displayed in the display area 2601. In this case, it is possible to overlook the film thickness distribution depending on the position. The film thickness can be recognized, for example, by comparing the contrast between the contrast bar 2602 and the film thickness distribution display area 2601. In the example of FIG. 26, it can be seen that the upward direction is thin, and the thickness increases as it goes downward. Note that an accurate numerical value or the like may be displayed as shown in FIGS. 20 to 25 by bringing a cursor or an average area on the film thickness distribution display area 2601. In this case, it is possible to recognize both the overall trend and the detailed numerical value.

  As described above, the regions 201 to 205 of the transmission electron beam detector 206 used for the film thickness monitor are automatically selected according to the element and the like and the film thickness (signal amount). It is also important to show the user whether or not It is also desirable that the user can specify which area of the areas 201 to 205 is to be used. Therefore, FIG. 27 shows a GUI display example of the light receiving region of the transmission electron detector.

  A molecule use area display unit 2701 in FIG. 27 displays an area used for a calculation molecule. In the example of FIG. 27, the molecule use area display unit 2701 is a BF1 signal in which the area 201 is selected. On the other hand, the denominator use area display unit 2702 displays an area used for the denominator of calculation, and in this example, the DF3 signal is selected from the area 205. While displaying the region of the detector thus selected, the user designates the region of the detector by selecting the region of the numerator use region display unit 2701 and the denominator use region display unit 2702 with the cursor. It is also possible. Furthermore, as shown in the example of the denominator use area display unit 2801 in FIG. 28, addition of a plurality of areas can be used for the denominator and the like. The same applies to the molecule use area display section.

  In this example, the arithmetic processing between the signals of the areas 201 to 205 selected in this way is performed by a semiconductor device included in the transmission electron detector control device 114. For this reason, high-speed real-time processing is possible. However, it is possible to perform calculation as software processing on the central processing unit 117, for example, without performing the calculation in hardware as described above. In this case, various arithmetic processing variations can be added by changing the program.

  As described above, in the charged particle beam apparatus according to the present embodiment, it is possible to accurately monitor the film thickness of the sample to be ion beam processed, so that high-precision observation and preparation of an analysis sample are possible.

  In this embodiment, a charged particle beam apparatus capable of extracting a minute sample piece from an original sample by ion beam processing will be described. Hereinafter, the difference from the first embodiment will be mainly described.

  FIG. 29 shows a configuration example of a charged particle beam apparatus with a function of extracting a small sample piece. The original sample stage 2901 can place an original sample 2902 such as a semiconductor wafer, a chip or a lump. A probe 2903 for extracting a sample piece from the original sample 2902 is held at the tip of the probe driving mechanism 2904. A probe controller 2905 controls the probe position and the like. An assist gas source 2906 that supplies an assist gas used for ion beam assist deposition or ion beam assist etching is controlled by a gas source control device 2907. The probe control device 2905, the gas source control device 2907, and the like are controlled by the central processing unit 117. Instead of the probe, a microfork that can sandwich the sample piece or a micromanipulator that can hold the sample piece may be used.

  Here, the production of a thin film from a minute sample piece extracted by ion beam processing will be described with reference to FIGS. FIG. 30 shows a flow of extracting a small sample piece.

  (A, b) First, three rectangular holes 3002, 3003, and 3004 are processed by the ion beam 3001 around the desired cross section (in the three side directions) of the original sample 2902 placed on the original sample stage 2901.

  (C) Next, the sample piece 3007 supported by the original sample 2902 only by the support part 3006 is produced by inclining the original sample stand 2901 and performing the groove 3005 processing.

  (D, e) Next, the inclination of the original sample stage 2901 is returned to the original position, and the tip of the probe 2903 is brought into contact with the sample piece 3007 by the probe driving mechanism 2904. A deposition film 3009 (a tungsten film in this embodiment) is formed by irradiating an ion beam 3001 to a region including the probe tip while supplying a deposition gas 3008 from an assist gas source 2906, and a sample piece. 3007 and the probe 2903 are fixed.

  (F, g) After fixing the sample piece 3007 and the probe 2903, the support portion 3006 is removed by ion beam processing to separate the sample piece 3007 from the original sample 2902.

  (H) The separated sample piece 3007 is brought into contact with the sample carrier 3010 by driving the probe. This sample carrier 3010 is placed on the sample stage 102 of FIG. Therefore, a deposition film 3011 is formed on the contact portion by the same method as described above, and the sample piece 3007 and the sample carrier 3010 are fixed.

  (I) After fixing the sample piece 3007 and the sample carrier 3010, the tip of the probe is subjected to ion beam processing to separate the probe, thereby making the sample piece 3007 independent of the probe.

  Next, production of a thin film will be described with reference to FIGS.

  (A, b) The ion beam 3001 is irradiated in parallel to the desired cross section and processed to near the desired cross section.

  (C) Further, the opposite side is irradiated with the ion beam 3001 and processed to the vicinity of the desired cross section.

  While repeating the above (b) and (c), both sides are FIB processed little by little to finish the target thin film. A thin film sample having a desired film thickness can be prepared by irradiating the thin film portion with an electron beam as shown in Example 1 and monitoring the film thickness during or between the thin film processes. It becomes possible. Further, when the thin film processing of FIGS. 31 (b) and (c) is automatically performed, the processing of FIGS. 31 (b) and (c) is automatically repeated until the film thickness is set in advance, and the film thickness set in advance is set. If the film thickness monitor information matches, the processing, that is, ion beam irradiation is stopped.

  Since the sample piece as shown in the present embodiment can be held on the thin sample carrier 3010, the possibility of shielding the electron beam transmission for film thickness monitoring is reduced, and accurate film thickness monitoring is facilitated. Can be done. This also has an effect on element information acquisition by X detection described in the first embodiment, and it is less likely that wrong element information is obtained by irradiating scattered electrons in the vicinity region. Film thickness measurement can be realized. In addition, since it is possible to perform operations such as processing a sample with a precise film thickness for a desired observation section from a large original sample in a single vacuum sample chamber, a sample that changes in quality by reacting with the atmosphere. In this case, a thin film sample can be reliably produced, and the processing throughput can be improved.

  In this embodiment, a charged particle beam apparatus using a gas ion beam for thin film finishing will be described. Hereinafter, the difference from the first and second embodiments will be mainly described.

  FIG. 32 shows a configuration example of a charged particle beam apparatus with a gas ion beam. A gas ion beam optical system 3201 that irradiates the sample 101 with a gas ion beam is controlled by a gas ion beam optical system controller 3202. The gas ion beam optical system control device 3202 is controlled from the central processing unit 117 in the same manner as other control device devices.

  Currently, a gallium ion beam is generally used as the ion beam 104 used for thin film processing. This is because the focusability of the gallium ion beam is excellent and it is effective for microfabrication. However, since gallium itself is a heavy metal, it is not preferable for analysis or the like that gallium remains in the processed sample. Furthermore, in order to focus the beam finely, high acceleration is necessary, but when processing with a high acceleration ion beam, a layer called a damage layer is formed. For example, when the sample to be processed is a silicon crystal, if the sample is processed with an accelerated gallium ion beam of about 30 kV, the silicon crystal is broken and an amorphous layer of about 30 nm is formed on one side.

  In order to remove such a heavy metal contaminated layer and damaged layer, it is effective to perform finishing with a low-acceleration gas ion beam. For example, argon or xenon is often used as the gas ion. The thin film is irradiated with these gas ions at a low acceleration of, for example, 1 kV or less and finished.

  This is shown in FIG. The sample thin film is irradiated with a gas ion beam 3301 and the region 3302 is irradiated. At present, it is difficult to narrow down the irradiation region of the gas ion beam as small as the gallium ion beam. Therefore, after forming a thin film with the gallium ion beam, the gas ion beam is widely irradiated as a final finish. In this case, since it is difficult to accurately position the irradiation position of the gas ion beam like the gallium ion beam, the processing is controlled not by the irradiation position management but by the time management. Here, by performing film thickness monitoring by transmission electrons described in the first and second embodiments, it is possible to acquire film thickness information during and between gas ion beam irradiations. Finishing process management can be realized by stopping the gas ion beam irradiation when the preset film thickness matches the film thickness monitor information.

  By adopting the apparatus configuration as shown in the present embodiment, the finishing end point can be controlled, so that higher quality thin film production can be realized.

  The present invention contributes to improvement of semiconductor device failure analysis and structure analysis technology. The present invention can be used not only for semiconductor devices but also for high-resolution observation of steel, light metals, polymer polymers, biological samples, and the like.

  In the above-described embodiments, the merit that a sample having an accurate film thickness can be produced by an apparatus in which ion beam processing and a film thickness monitor are integrated has been described. The present invention can also be used for an apparatus for measuring the film thickness of a sample manufactured by another ion beam apparatus or a sample manufactured by mechanical polishing, chemical polishing, or the like.

101, 501, 601, 1201, 1301 Sample 102 Sample stage 103 Sample position controller 104, 3001 Ion beam 105 Ion beam optical system 106 Ion beam optical system controller 107 Secondary electron detector 108 Secondary electron detector controller 109 Electron beam 110 Electron beam optical system 111 Electron beam optical system controller 112, 502, 1202 Transmitted electron beam 113 Transmitted electron detector 114 Transmitted electron detector controller 115 X-ray detector 116 X-ray detector controller 117 Central processing unit 118 Display devices 201 to 205, 301 to 305, 1801 to 1805, 1901, 1902, 3302 Region 206 Detectors 701, 702, 801 to 805, 901, 902, 1001, 1002, 1101, 1401 to 1403, 1501 to 1503 1601, 603, 1701, 1703 Signal intensity 1602 Thin area 1702 Thick area 1903 Element input area 2001 Secondary electron image 2002 Cursor 2003, 2302 Film thickness display area 2101 Meter display area 2201 Pop-up 2301 Monitor area 2601 Film thickness distribution display area 2602 Contrast bar 2701 Molecule use region display unit 2702, 2803 Denominator use region display unit 2902 Original sample 2903 Probe 2904 Probe drive mechanism 2905 Probe control device 2906 Assist gas source 2907 Gas source control device 3002 to 3004 Rectangular hole 3005 Groove 3006 Support unit 3007 Sample piece 3008 Position gas 3009, 3011 Deposition film 3010 Sample carrier 3202 Gas ion beam optical system controller 3301 Gas ion beam

Claims (26)

In a charged particle beam apparatus having an electron beam optical system for irradiating an electron beam, a sample stage on which a sample is placed, and a transmission electron detector for detecting transmitted electrons,
The detection unit of the transmission electron detector is divided into a plurality of regions,
A calculation mechanism for calculating the intensity ratio of the transmission electron beam detected by the first region and the transmission electron beam detected by the second region in the plurality of regions;
A charged particle beam apparatus comprising: a display device that displays a film thickness of the sample. The charged particle beam apparatus according to claim 1,
The calculation mechanism is characterized in that a transmission electron beam intensity detected by a region detecting a transmission electron beam having a small scattering angle is divided by a transmission electron beam intensity detected by a region detecting a transmission electron having a large scattering angle. Charged particle beam device. The charged particle beam apparatus according to claim 1,
When the transmission electron beam detection detected by the first region and / or the second region becomes a predetermined condition, the arithmetic mechanism determines the first region and / or the second region. A charged particle beam device characterized by being changed. The charged particle beam apparatus according to claim 1,
The charged particle beam apparatus according to claim 1, wherein the calculation mechanism changes the first region and / or the second region based on a constituent element of a sample at a location irradiated with an electron beam. The charged particle beam apparatus according to claim 1,
A charged particle beam apparatus comprising a spectroscopic detector for detecting a constituent element of the sample. The charged particle beam device according to claim 5, wherein
A charged particle beam apparatus, wherein the spectroscopic detector is an X-ray detector. The charged particle beam apparatus according to claim 1,
A charged particle beam apparatus comprising an input device for inputting a constituent element of the sample. The charged particle beam apparatus according to claim 1,
The charged particle beam apparatus, wherein the display device displays an average film thickness in a desired region of the sample. The charged particle beam apparatus according to claim 1,
The charged particle beam device, wherein the display device displays a film thickness distribution in a desired region of the sample. The charged particle beam apparatus according to claim 1,
A charged particle beam apparatus comprising an ion beam optical system for irradiating the sample with an ion beam. The charged particle beam apparatus according to claim 10, wherein
The ion beam optical system controls ion beam irradiation based on an output of the calculation mechanism. The charged particle beam apparatus according to claim 10, wherein
A charged particle beam apparatus capable of simultaneously irradiating an ion beam and an electron beam. The charged particle beam apparatus according to claim 10, wherein
A charged particle beam apparatus comprising a transfer mechanism for transferring a sample piece separated from an original sample by ion beam processing. A method for measuring a film thickness of a sample,
An electron beam optical system irradiates the sample with an electron beam,
By the transmission electron detector divided into a plurality of areas, the detection unit detects the transmission electron beam that has passed through the sample,
With the calculation device, the intensity ratio of the transmission electron beam detected by the first region and the transmission electron beam detected by the second region in the plurality of regions is calculated,
A film thickness measuring method for displaying the film thickness of the sample by a display device. In the film thickness measuring method according to claim 14,
By the calculation mechanism, the transmission electron beam intensity detected by the region detecting the transmission electron beam having a small scattering angle is divided by the transmission electron beam intensity detected by the region detecting the transmission electron having a large scattering angle. Film thickness measurement method. In the film thickness measuring method according to claim 14,
The first region and / or the second region is changed when transmission electron beam detection detected by the first region and / or the second region becomes a predetermined condition. The film thickness measuring method. In the film thickness measuring method according to claim 14,
A film thickness measuring method, wherein the first region and / or the second region is changed based on a constituent element of a sample at a location irradiated with an electron beam. In the film thickness measuring method according to claim 14,
A method for measuring a film thickness, wherein a constituent element of the sample is detected by a spectroscopic detector. The film thickness measuring method according to claim 18 ,
The film thickness measuring method, wherein the spectral detector is an X-ray detector. In the film thickness measuring method according to claim 14,
A method for measuring a film thickness, wherein the constituent elements of the sample are input to the arithmetic device by an input device. In the film thickness measuring method according to claim 14,
An average film thickness in a desired region of the sample is displayed. In the film thickness measuring method according to claim 14,
A film thickness measuring method, comprising displaying a film thickness distribution in a desired region of the sample. In the film thickness measuring method according to claim 14,
A film thickness measuring method comprising irradiating an ion beam to the sample by an ion beam optical system to form a thin film on the sample. The film thickness measuring method according to claim 23,
The film thickness measuring method, wherein the ion beam optical system controls irradiation of an ion beam based on an output of the calculation mechanism. The film thickness measuring method according to claim 23,
A method for measuring a film thickness, comprising simultaneously forming a thin film on the sample by ion beam irradiation and measuring a thin film by electron beam irradiation. The film thickness measuring method according to claim 23 ,
A method of measuring a film thickness, comprising measuring a film thickness of a sample piece separated from an original sample by ion beam processing.

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